In recent years, a large number of fibers have been used in interior materials for automobiles, airplanes, railroads and buildings and filter materials, and fiber materials such as synthetic fibers including polyester, nylon, acrylonitrile and polypropylene fibers, cellulose-based fibers including rayon, cotton and hemp fibers, and animal fibers including woolen, silk and feather fibers have been used alone or in combination.
Since fiber products comprising these fibers have a defect that they are highly combustible, flameproofing performance is required for these products. For example, flame-retardant fibers are used in some fields such as uniforms for airplane pilots, and post-processing flameproofing is generally carried out on the fibers from the viewpoint of cost.
Typical examples of post-processing flameproofing include a method in which a flameproofing agent is directly adhered to a fiber product and a method in which a flameproofing agent is added to synthetic fiber binders and adhered as a flameproofing binder. These methods are generally employed for sheets for chair upholstery for automobiles, airplanes and railcars or backing for carpets. Especially in the latter flameproofing method, it is necessary to flameproof not only fibers but also a synthetic resin binder used in combination.
A halogen-based compound or a combination of a halogen-based compound and antimony oxide has been used as a flameproofing agent. However, in recent years, demand for flameproofing without using a halogen-based flameproofing agent has been growing due to environment conservation and the harmful effect of a gas generated at the time of combustion. As a halogen-free flameproofing agent, there are known a large number of flameproofing agents such as ammonium phosphate, ammonium sulfamate, ammonium sulfate, pyrobate, boric acid, aluminum hydroxide, magnesium hydroxide and phosphoric acid esters.
However, when the flameproofing agent is added in an amount required for producing a flameproofing effect, a water-soluble flameproofing agent causes problems such as the thickening of a synthetic resin emulsion, the occurrence of destruction (gum-up), the reduction of the strength of a resin film, the degradation of heat resistance and the deterioration of texture. Since ammonium polyphosphate which is halogen-free and has a flameproofing effect relatively has solubility in water, it elutes into water under conditions under which water resistance is required, thereby causing problems with the physical properties and flameproofness of a product. Further, even ammonium polyphosphate which is capsulated with an improved resin is unsatisfactory in terms of water resistance. Therefore, a flameproofing method which provides satisfactory flameproofness and physical properties without using a halogen-based flameproofing agent is not provided and the development of such a method is desired (patent documents 1 to 3).
(Patent Document 1) JP-A 10-212669
(Patent Document 2) JP-A 2002-220782
(Patent Document 3) Japan Patent No. 3484490